Candidate: Warren R. Dunn, MD, MPH, Assistant Professor of Orthopaedics at Vanderbilt University with a secondary appointment as Assistant Professor in the Department of Medicine & Public Health at the Center for Health Services Research. He completed the American Academy of Orthopaedic Surgeons / Orthopaedic Research and Education Foundation Health Services Research Fellowship at the Hospital for Special Surgery on the Sports Medicine and Shoulder Service. In this K23 application he proposes a comprehensive five-year career development plan that includes advanced coursework and training in clinical epidemiology, biostatistics, clincal trial design, and to conduct a mentored research project investigating outcomes after anterior cruciate ligament (ACL) reconstruction in order to achieve the goal of becoming an independent surgeon scientist. Project Rationale: Physical activity and fitness is one of the focus areas of Healthy People 2010, and sports participation is increasing. In accord, the number of ACL injuries and subsequent ACL reconstructions is increasing at an estimated annual cost of 2 billion dollars. Available evidence shows that ACL reconstructions have been successful in restoring preoperative function at two years, but these studies have utilized non-validated outcome measures, often lack long-term follow-up, and have left risk factors for poor outcome, graft failure, and additional surgical procedures ill defined. Design: A multi-center observational cohort study involving an established Multi-center Orthopaedic Outcomes Network (MOON) will be utilized. The purpose of the proposed mentored research is to test the hypothesis that objective predictors recorded at the time of ACL reconstruction are associatedwith validated outcome instruments and arthritis (Aim 1), and additional surgical procedures and graft failure (Aim 2). Vanderbilt is a robust academic environment capable of providing the education, training, and mentorship necessary to enable Dr. Dunn to become an independent patient-oriented clinician scientist. The ACL is the most frequently injured ligament in the body, and disruption of this important stablizer leads to giving way episodes that cause further injury to the knee. ACL reconstruction restores stability to the knee, however, it is unclear if surgery prevents later arthritis of the knee. Identifying factors associated with quality of life and arthritis is critical because arthritis, particularly in young adults, is a major public health concern.